前文介紹了代理模式及實(shí)現(xiàn)，但想要實(shí)現(xiàn)一個(gè)完整的AOP框架還遠(yuǎn)遠(yuǎn)不夠，接下來(lái)我們來(lái)分析一下Spring是如何實(shí)現(xiàn)AOP的棺弊。
1 AOP體系結(jié)構(gòu)
下圖AOP聯(lián)盟定義的AOP體系結(jié)構(gòu)，大致分為從使用到實(shí)現(xiàn)的三個(gè)層次瞬女。整篇文章都將按照這三個(gè)層次進(jìn)行分析
1.1 層次3:語(yǔ)言和開發(fā)環(huán)境
- 基礎(chǔ):可以視為待增強(qiáng)對(duì)象
- 切面:通常包含對(duì)于基礎(chǔ)的增強(qiáng)應(yīng)用
- 配置:指配置環(huán)境或編織配置,將基礎(chǔ)和切面結(jié)合起來(lái)，從而實(shí)現(xiàn)對(duì)目標(biāo)對(duì)象的編織實(shí)現(xiàn)
Spring使用Java語(yǔ)言來(lái)實(shí)現(xiàn)增強(qiáng)對(duì)象和切面努潘，并為這兩者提供配置環(huán)境;對(duì)于編織配置诽偷，可以使用IoC容器來(lái)完成，而Ioc恰恰是Spring的強(qiáng)項(xiàng)疯坤。
1.2 層次2:面向方面系統(tǒng)
面向方面系統(tǒng)為上層的語(yǔ)言與開發(fā)環(huán)境提供支持报慕，將基礎(chǔ)、切面和配置封裝成面向方面中的邏輯模型压怠。
1.3 層次1:底層編織實(shí)現(xiàn)模塊
將編織邏輯進(jìn)行實(shí)現(xiàn)的技術(shù)眠冈。
前文所述的兩種動(dòng)態(tài)代理技術(shù)就是在這個(gè)層面進(jìn)行應(yīng)用。
2 Spring AOP實(shí)現(xiàn)
我們從上到下的看看Spring如何實(shí)現(xiàn)AOP的菌瘫。整個(gè)AOP框架邏輯流程很復(fù)雜蜗顽，這里就只對(duì)在目標(biāo)對(duì)象在單例模式下并使用JDK動(dòng)態(tài)代理的AOP進(jìn)行分析布卡。
2.1 層次3:語(yǔ)言和開發(fā)環(huán)境
2.1.1 基礎(chǔ)
在Spring中，基礎(chǔ)就是你配置的Bean對(duì)象雇盖，這個(gè)Bean對(duì)象可以配置在XML中忿等，也可以使用注解進(jìn)行配置,如<bean id="realSubject" class="com.magicalwolf.proxy.RealSubject" />
2.1.2 切面
在Spring中，切面由切點(diǎn)和通知組成崔挖，由使用者進(jìn)行定義.
PointCut切點(diǎn)
決定Advice通知應(yīng)該作用于哪個(gè)連接點(diǎn)贸街，也就是通過(guò)切點(diǎn)定義哪些方法需要增強(qiáng)。
PointCut接口是所有切點(diǎn)實(shí)現(xiàn)的基本接口狸相，其中定義了MethodMatcher方法薛匪，用來(lái)判斷當(dāng)前方法是否需要增強(qiáng)【砹ǎ可以通過(guò)不同的方式進(jìn)行判斷蛋辈，如JdkRegexpMethodPointcut類使用正則表達(dá)式進(jìn)行匹配属拾，還可以使用類限定名将谊，切點(diǎn)表達(dá)式等方式進(jìn)行匹配。
Advice通知
通知定義在連接點(diǎn)做什么渐白，為切面增強(qiáng)提供織入接口尊浓。Advice接口是AOP聯(lián)盟定義的統(tǒng)一接口，Spring對(duì)這個(gè)接口進(jìn)行了細(xì)化和擴(kuò)展纯衍，如BeforeAdvice,AfterAdvice,ThrowsAdvice
Advisor通知器
通知器將通知和切點(diǎn)結(jié)合起來(lái)栋齿，為Spring配置AOP容器提供便利。
2.1.3 配置
對(duì)基礎(chǔ)和切面進(jìn)行配置襟诸，使之對(duì)基礎(chǔ)進(jìn)行增強(qiáng).Spring實(shí)現(xiàn)多種方式的配置瓦堵，ProxyFactoryBean完成聲明式配置，ProxyFactory完成編程式配置歌亲。AspectJProxyFactory將Spring和Aspectj集成菇用。
2.1.4 使用ProxyFactoryBean的示例
applicationContext.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:context="http://www.springframework.org/schema/context" xmlns="http://www.springframework.org/schema/beans"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<!-- 目標(biāo)對(duì)象 -->
<bean id="realSubject" class="com.magicalwolf.proxy.RealSubject" />
<!-- 通知 -->
<bean id="requestAdvice" class="com.magicalwolf.spring.aop.RequestBeforeAdvice" />
<!-- 通知器 -->
<bean id="requestAdvisor"
class="org.springframework.aop.support.NameMatchMethodPointcutAdvisor">
<property name="advice">
<ref bean="requestAdvice" />
</property>
<property name="mappedName">
<value>request</value>
</property>
</bean>
<!-- 代理工廠 -->
<bean id="requestAOP" class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="proxyInterfaces" value="com.magicalwolf.proxy.Subject" />
<property name="target">
<ref bean="realSubject" />
</property>
<property name="interceptorNames">
<list>
<value>requestAdvisor</value>
</list>
</property>
</bean>
</beans>
RequestBeforeAdvice.java
public class RequestBeforeAdvice implements MethodBeforeAdvice{
private void before(String param) throws Throwable{
if(!param.equals("magicalwolf"))
throw new IllegalArgumentException();
}
@Override
public void before(Method method, Object[] args, Object target)
throws Throwable {
before((String)args[0]);
}
}
Main.java
public class Main {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
Subject proxy= (Subject) context.getBean("requestAOP");
proxy.request("magicalwolf");
proxy.request("hello");
}
}
層次3主要定義了開發(fā)人員如何使用AOP，Spring在背后將進(jìn)行邏輯模型的封裝工作
2.2 層次2:面向方面系統(tǒng)
我們從ProxyFactoryBean出發(fā)陷揪，看看面向方面系統(tǒng)是如何對(duì)target目標(biāo)起作用的惋鸥。
2.2.1 ProxyFactoryBean的繼承關(guān)系
-
ProxyFactoryBean類負(fù)責(zé)具體AOP代理對(duì)象的生成 -
ProxyCreateSupport類是創(chuàng)建AOP代理對(duì)象的一個(gè)輔助類 -
AdvisedSupport類封裝了對(duì)通知和通知器相關(guān)的操作 -
ProxyConfig類為子類提供配置屬性
2.2.2 生成代理對(duì)象跟蹤
從FactoryBean中獲取對(duì)象，是以getObject()方法為入口悍缠，在ProxyFactoryBean也是如此卦绣，getObject()方法對(duì)目標(biāo)對(duì)象進(jìn)行增強(qiáng)處理。
2.2.2.1 public Object getObject()
首先對(duì)通知器鏈進(jìn)行初始化飞蚓，生成代理對(duì)象時(shí)如果是單例模式調(diào)用getSingletonInstance(),此處只分析單例的情況
public Object getObject() throws BeansException {
initializeAdvisorChain();//初始化通知器鏈(2.2.2.2)
if (isSingleton()) {
return getSingletonInstance();//生成Singleton的代理對(duì)象(2.2.2.3)
}
else {
if (this.targetName == null) {
logger.warn("Using non-singleton proxies with singleton targets is often undesirable. " +
"Enable prototype proxies by setting the 'targetName' property.");
}
return newPrototypeInstance();
}
}
2.2.2.2 private synchronized void initializeAdvisorChain()
初始化通知器鏈滤港，此方法是線程安全的
private synchronized void initializeAdvisorChain() throws AopConfigException, BeansException {
if (this.advisorChainInitialized) {
return;
}
/檢查interceptorNames是否為空，interceptorNames是一個(gè)String[]
if (!ObjectUtils.isEmpty(this.interceptorNames)) {
//檢查beanFactory是否為null趴拧，此處的beanFactory是Spring的Bean工廠,直接從容器中獲得配置的通知器
if (this.beanFactory == null) {
throw new IllegalStateException("No BeanFactory available anymore (probably due to serialization) " +
"- cannot resolve interceptor names " + Arrays.asList(this.interceptorNames));
}
// Globals can't be last unless we specified a targetSource using the property...
if (this.interceptorNames[this.interceptorNames.length - 1].endsWith(GLOBAL_SUFFIX) &&
this.targetName == null && this.targetSource == EMPTY_TARGET_SOURCE) {
throw new AopConfigException("Target required after globals");
}
// 通過(guò)Bean Name獲得通知器
for (String name : this.interceptorNames) {
if (logger.isTraceEnabled()) {
logger.trace("Configuring advisor or advice '" + name + "'");
}
//GLOBAL_SUFFIX = "*"蜗搔，說(shuō)明這個(gè)通知器是全局通知器
if (name.endsWith(GLOBAL_SUFFIX)) {
if (!(this.beanFactory instanceof ListableBeanFactory)) {
throw new AopConfigException(
"Can only use global advisors or interceptors with a ListableBeanFactory");
}
addGlobalAdvisor((ListableBeanFactory) this.beanFactory,
name.substring(0, name.length() - GLOBAL_SUFFIX.length()));
}
else {
// 添加一個(gè)命名的通知器劲藐，檢查是singleton還是prototype
Object advice;
if (this.singleton || this.beanFactory.isSingleton(name)) {
// 獲得一個(gè)Advice或Advisor
advice = this.beanFactory.getBean(name);
}
else {
// It's a prototype Advice or Advisor: replace with a prototype.
// Avoid unnecessary creation of prototype bean just for advisor chain initialization.
advice = new PrototypePlaceholderAdvisor(name);
}
addAdvisorOnChainCreation(advice, name);//添加通知器到通知器列表(2.2.6)
}
}
}
this.advisorChainInitialized = true;
}
2.2.2.3 private synchronized Object getSingletonInstance()
private synchronized Object getSingletonInstance() {
//singletonInstance為緩存的單例對(duì)象，如果存在就直接返回
if (this.singletonInstance == null) {
this.targetSource = freshTargetSource();//targetSource在AdvisedSupport中定義樟凄，用來(lái)獲得目標(biāo)對(duì)象
if (this.autodetectInterfaces && getProxiedInterfaces().length == 0 && !isProxyTargetClass()) {
//依靠AOP框架告訴我們哪個(gè)接口被代理
Class<?> targetClass = getTargetClass();
if (targetClass == null) {
throw new FactoryBeanNotInitializedException("Cannot determine target class for proxy");
}
//設(shè)置代理接口聘芜，在AdvisedSupport中定義了interfaces列表
setInterfaces(ClassUtils.getAllInterfacesForClass(targetClass, this.proxyClassLoader));
}
super.setFrozen(this.freezeProxy);
//使用ProxyFactory生成需要的Proxy
this.singletonInstance = getProxy(createAopProxy());
//getProxy（2.2.2.4），createAopProxy(2.2.2.5)
}
return this.singletonInstance;
}
2.2.2.4 protected Object getProxy(AopProxy aopProxy)
AopProxy是一個(gè)接口缝龄，有兩個(gè)子類實(shí)現(xiàn)汰现，一個(gè)是ObjenesisCglibAopProxy,一個(gè)是JdkDynamicProxy.分別通過(guò)CGLIB和JDK來(lái)生成需要的Proxy代理對(duì)象
protected Object getProxy(AopProxy aopProxy) {
//通過(guò)AopProxy得到代理對(duì)象
return aopProxy.getProxy(this.proxyClassLoader);
}
2.2.2.5 protected final synchronized AopProxy createAopProxy()
此方法在ProxyCreatorSupport中定義，具體是通過(guò)AopProxyFactory來(lái)獲得AopProxy叔壤，AopProxyFactory默認(rèn)的工廠實(shí)現(xiàn)是DefaultAopProxyFactory瞎饲，生成哪一種AopProxy就在此類中定義
protected final synchronized AopProxy createAopProxy() {
if (!this.active) {
activate();
}
return getAopProxyFactory().createAopProxy(this);
}
DefaultAopProxyFactory中的createAopProxy方法
public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {
if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) {
Class<?> targetClass = config.getTargetClass();
//檢查目標(biāo)對(duì)象是否存在
if (targetClass == null) {
throw new AopConfigException("TargetSource cannot determine target class: " +
"Either an interface or a target is required for proxy creation.");
}
//如果是接口類使用JDK生成Proxy
if (targetClass.isInterface()) {
return new JdkDynamicAopProxy(config);
}
//否則用cglib
return new ObjenesisCglibAopProxy(config);
}
else {
return new JdkDynamicAopProxy(config);
}
}
JdkDynamicAopProxy中的getObject方法，這里我們可以看到熟悉的Proxy.newProxyInstance()方法
public Object getProxy(ClassLoader classLoader) {
if (logger.isDebugEnabled()) {
logger.debug("Creating JDK dynamic proxy: target source is " + this.advised.getTargetSource());
}
Class<?>[] proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised);
findDefinedEqualsAndHashCodeMethods(proxiedInterfaces);
return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this);
}
2.2.2.6 private void addAdvisorOnChainCreation(Object next, String name)
namedBeanToAdvisor方法會(huì)將next對(duì)象包裝為Advisor對(duì)象炼绘，并添加到Advisor集合中
private void addAdvisorOnChainCreation(Object next, String name) {
Advisor advisor = namedBeanToAdvisor(next);
if (logger.isTraceEnabled()) {
logger.trace("Adding advisor with name '" + name + "'");
}
addAdvisor(advisor);
}
在namedBeanToAdvisor方法中嗅战，會(huì)使用DefaultAdvisorAdapterRegistry的warp方法對(duì)next對(duì)象進(jìn)行包裝.通知器是由切點(diǎn)和通知組成，如果只配置了通知俺亮，則切點(diǎn)為默認(rèn)的TruePointcut,它對(duì)任何方法的匹配都將返回true
public Advisor wrap(Object adviceObject) throws UnknownAdviceTypeException {
//如果對(duì)象已經(jīng)是Advisor直接返回
if (adviceObject instanceof Advisor) {
return (Advisor) adviceObject;
}
//檢查類型
if (!(adviceObject instanceof Advice)) {
throw new UnknownAdviceTypeException(adviceObject);
}
Advice advice = (Advice) adviceObject;
if (advice instanceof MethodInterceptor) {
// 包裝為默認(rèn)切點(diǎn)通知器
return new DefaultPointcutAdvisor(advice);
}
for (AdvisorAdapter adapter : this.adapters) {
// 檢查是否匹配
if (adapter.supportsAdvice(advice)) {
return new DefaultPointcutAdvisor(advice);
}
}
throw new UnknownAdviceTypeException(advice);
}
通過(guò)以上的分析驮捍，我們已經(jīng)得到了代理對(duì)象，至此層次2的工作已經(jīng)完成了脚曾，層次3獲得的配置模型东且，在配置邏輯的應(yīng)用下向AOP模型轉(zhuǎn)換，接下來(lái)該層次1的實(shí)現(xiàn)了
2.2 層次1:底層編織實(shí)現(xiàn)模塊
在生成代理對(duì)象的時(shí)候本讥，相關(guān)的攔截器已經(jīng)配置完成珊泳，攔截器起作用是通過(guò)對(duì)方法進(jìn)行回掉完成的。
2.2.1 使用JDK代理的實(shí)現(xiàn)
前文提到過(guò)拷沸，在JDK代理中方法回掉的入口是在invoke方法中色查。而JdkDynamicAopProxy實(shí)現(xiàn)了InvocationHandler接口，方法回掉邏輯也定義在其中.
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
MethodInvocation invocation;
Object oldProxy = null;
boolean setProxyContext = false;
TargetSource targetSource = this.advised.targetSource;
Class<?> targetClass = null;
Object target = null;
try {
if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {
// 目標(biāo)沒(méi)有實(shí)現(xiàn)自己的equals方法
return equals(args[0]);
}
if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {
// 目標(biāo)沒(méi)有實(shí)現(xiàn)自己的hashCodes方法
return hashCode();
}
if (!this.advised.opaque && method.getDeclaringClass().isInterface() &&
method.getDeclaringClass().isAssignableFrom(Advised.class)) {
// 根據(jù)代理對(duì)象的配置調(diào)用服務(wù)撞芍，如果是Advised接口的實(shí)現(xiàn)類秧了，則直接調(diào)用
return AopUtils.invokeJoinpointUsingReflection(this.advised, method, args);
}
Object retVal;
if (this.advised.exposeProxy) {
// Make invocation available if necessary.
oldProxy = AopContext.setCurrentProxy(proxy);
setProxyContext = true;
}
// 有可能為null.盡可能減少擁有目標(biāo)對(duì)象的時(shí)間，在這種情況下對(duì)象來(lái)自于對(duì)象池
target = targetSource.getTarget();
if (target != null) {
targetClass = target.getClass();
}
// 獲得這個(gè)方法的連接器鏈
List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);//2.2.2
//如果沒(méi)有攔截器鏈勤庐，則直接調(diào)用目標(biāo)對(duì)象
if (chain.isEmpty()) {
retVal = AopUtils.invokeJoinpointUsingReflection(target, method, args);
}
else {
// 構(gòu)造一個(gè)方法調(diào)用
invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
// 調(diào)用連接點(diǎn)的攔截器鏈(2.2.3)
retVal = invocation.proceed();
}
Class<?> returnType = method.getReturnType();
if (retVal != null && retVal == target && returnType.isInstance(proxy) &&
!RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) {
retVal = proxy;
}
else if (retVal == null && returnType != Void.TYPE && returnType.isPrimitive()) {
throw new AopInvocationException(
"Null return value from advice does not match primitive return type for: " + method);
}
return retVal;
}
finally {
if (target != null && !targetSource.isStatic()) {
// 必須來(lái)自TargetSource.
targetSource.releaseTarget(target);
}
if (setProxyContext) {
// 重新保存舊的代理
AopContext.setCurrentProxy(oldProxy);
}
}
}
invoke方法獲取目標(biāo)對(duì)象和攔截器鏈示惊，并生成ReflectiveMethodInvocation對(duì)象，通過(guò)這個(gè)對(duì)象完成對(duì)AOP功能的封裝愉镰。
2.2.2 獲得方法的攔截器鏈
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(Method method, Class<?> targetClass) {
MethodCacheKey cacheKey = new MethodCacheKey(method);
List<Object> cached = this.methodCache.get(cacheKey);//
if (cached == null) {
cached = this.advisorChainFactory.getInterceptorsAndDynamicInterceptionAdvice(
this, method, targetClass);
this.methodCache.put(cacheKey, cached);
}
return cached;
}
methodCache是一個(gè)集合Map<MethodCacheKey, List<Object>>,對(duì)方法的攔截器鏈進(jìn)行緩存米罚，如果不在緩存中，則生成并添加丈探。這里使用DefaultAdvisorChainFactory來(lái)生成攔截器鏈
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(
Advised config, Method method, Class<?> targetClass) {
//通過(guò)config獲得配置好的advisor鏈录择，AdvisedSupport實(shí)現(xiàn)了Advised
List<Object> interceptorList = new ArrayList<Object>(config.getAdvisors().length);
//實(shí)際對(duì)象
Class<?> actualClass = (targetClass != null ? targetClass : method.getDeclaringClass());
//判斷是否符合配置要求
boolean hasIntroductions = hasMatchingIntroductions(config, actualClass);
AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();
for (Advisor advisor : config.getAdvisors()) {
if (advisor instanceof PointcutAdvisor) {
PointcutAdvisor pointcutAdvisor = (PointcutAdvisor) advisor;
//判斷通知器是否匹配實(shí)際對(duì)象
if (config.isPreFiltered() || pointcutAdvisor.getPointcut().getClassFilter().matches(actualClass)) {
MethodInterceptor[] interceptors = registry.getInterceptors(advisor);//將通知器適配成方法攔截
MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher();
if (MethodMatchers.matches(mm, method, actualClass, hasIntroductions)) {
if (mm.isRuntime()) {
for (MethodInterceptor interceptor : interceptors) {
//封裝成動(dòng)態(tài)方法匹配
interceptorList.add(new InterceptorAndDynamicMethodMatcher(interceptor, mm));
}
}
else {
interceptorList.addAll(Arrays.asList(interceptors));//將攔截器鏈添加到列表中
}
}
}
}
else if (advisor instanceof IntroductionAdvisor) {
IntroductionAdvisor ia = (IntroductionAdvisor) advisor;
if (config.isPreFiltered() || ia.getClassFilter().matches(actualClass)) {
Interceptor[] interceptors = registry.getInterceptors(advisor);
interceptorList.addAll(Arrays.asList(interceptors));
}
}
else {
Interceptor[] interceptors = registry.getInterceptors(advisor);
interceptorList.addAll(Arrays.asList(interceptors));
}
}
return interceptorList;
}
此方法有一個(gè)適配和注冊(cè)的過(guò)程，它將Advice通知適配成Spring預(yù)先設(shè)計(jì)好的攔截器。適配和注冊(cè)的工作是在GlobalAdvisorAdapterRegistry的getInterceptors()中完成的
public MethodInterceptor[] getInterceptors(Advisor advisor) throws UnknownAdviceTypeException {
List<MethodInterceptor> interceptors = new ArrayList<MethodInterceptor>(3);
Advice advice = advisor.getAdvice();//獲得通知
if (advice instanceof MethodInterceptor) {//如果是MethodInterceptor則直接添加
interceptors.add((MethodInterceptor) advice);
}
for (AdvisorAdapter adapter : this.adapters) {//遍歷注冊(cè)的適配器隘竭，檢查是否匹配
if (adapter.supportsAdvice(advice)) {
interceptors.add(adapter.getInterceptor(advisor));
}
}
if (interceptors.isEmpty()) {
throw new UnknownAdviceTypeException(advisor.getAdvice());
}
return interceptors.toArray(new MethodInterceptor[interceptors.size()]);
}
在GlobalAdvisorAdapterRegistry的構(gòu)造函數(shù)中注冊(cè)了三種適配器塘秦，注冊(cè)過(guò)程就是將這三種適配器加入List集合
public DefaultAdvisorAdapterRegistry() {
registerAdvisorAdapter(new MethodBeforeAdviceAdapter());
registerAdvisorAdapter(new AfterReturningAdviceAdapter());
registerAdvisorAdapter(new ThrowsAdviceAdapter());
}
來(lái)看一下MethodBeforeAdviceAdapter
class MethodBeforeAdviceAdapter implements AdvisorAdapter, Serializable {
@Override
public boolean supportsAdvice(Advice advice) {//是否支持
return (advice instanceof MethodBeforeAdvice);
}
@Override
public MethodInterceptor getInterceptor(Advisor advisor) {//將Advice適配成Interceptor
MethodBeforeAdvice advice = (MethodBeforeAdvice) advisor.getAdvice();
return new MethodBeforeAdviceInterceptor(advice);
}
}
將Advice封裝成了MethodBeforeAdviceInterceptor,此類中有invoke方法，會(huì)先調(diào)用advice的before方法
public Object invoke(MethodInvocation mi) throws Throwable {
this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis() );
return mi.proceed();
}
至此动看，Spring AOP實(shí)現(xiàn)了對(duì)advice的織入尊剔，可以看到它將xml中配置的通知器適配成了攔截器
2.2.3 方法調(diào)用
之前講到了攔截器的適配和注冊(cè)，對(duì)呀?jīng)]有攔截器的方法直接調(diào)用菱皆，有攔截器的方法會(huì)構(gòu)造ReflectiveMethodInvocation须误，并沿著攔截器鏈進(jìn)行調(diào)用。整個(gè)調(diào)用鏈的入口在proceed方法中
public Object proceed() throws Throwable {
//從索引為-1的攔截器開始仇轻，并遞增
//如果攔截器迭代調(diào)用完成京痢，則調(diào)用目標(biāo)方法
if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
return invokeJoinpoint();//使用invokeJoinpointUsingReflection調(diào)用目標(biāo)對(duì)象
}
//沿著攔截器鏈執(zhí)行
Object interceptorOrInterceptionAdvice =
this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {
//對(duì)方法進(jìn)行動(dòng)態(tài)匹配，切點(diǎn)的匹配就在這里進(jìn)行
InterceptorAndDynamicMethodMatcher dm =
(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;
if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {
return dm.interceptor.invoke(this);
}
else {
// 動(dòng)態(tài)匹配失敗
// 跳過(guò)這個(gè)攔截器調(diào)用下一個(gè)
return proceed();
}
}
else {
// 這是一個(gè)攔截器篷店，直接調(diào)用它
return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
}
}
至此祭椰，完成對(duì)攔截器鏈及目標(biāo)方法的調(diào)用
3 總結(jié)
3.1 層次3:語(yǔ)言與開發(fā)環(huán)境
Spring AOP使用Java語(yǔ)言，可以通過(guò)多種方式進(jìn)行AOP配置疲陕，基礎(chǔ)就是Bean對(duì)象方淤，切面可以通過(guò)xml或注解進(jìn)行聲明.配置是由IoC容器完成的
3.2 層次2:面向方面系統(tǒng)
本文分析使用ProxyFactoryBean的情況,ProxyFactoryBean處理配置邏輯，生成代理對(duì)象鸭轮。ProxyFactoryBean會(huì)先初始化通知器集合臣淤，再根據(jù)代理類型使用JdkDynamicProxy或ObjenesisCglibAopProxy生成代理對(duì)象
3.1 層次1:底層編織實(shí)現(xiàn)模塊
使用JDK代理中橄霉，方法的回掉入口在invoke方法中窃爷，在invoke方法中實(shí)現(xiàn)了Advice的織入，以及目標(biāo)方法的調(diào)用姓蜂。
對(duì)Advice的織入按厘，Spring預(yù)先設(shè)計(jì)好了攔截器，如MethodBeforeAdviceInterceptor,AfterReturningAdviceInterceptor,ThrowsAdviceInterceptor,將Advice適配成對(duì)應(yīng)的攔截器钱慢，并將攔截器鏈緩存,此時(shí)完成了對(duì)Advice的織入
對(duì)目標(biāo)方法的調(diào)用逮京，如果在目標(biāo)方法未配置攔截器，則直接調(diào)用目標(biāo)方法束莫，如果得到了攔截器鏈懒棉，則沿著攔截器鏈執(zhí)行。在執(zhí)行過(guò)程中如果是動(dòng)態(tài)匹配的攔截器览绿，則需要再次進(jìn)行匹配策严，否則直接調(diào)用攔截器。
以上分析了Spring AOP的部分實(shí)現(xiàn)饿敲，不過(guò)整個(gè)AOP基本流程已經(jīng)分析完成妻导。有了基礎(chǔ)再去看AOP的高級(jí)部分會(huì)更加容易
